Theoretical And Experimental Study On Ohmic Contacts To Silicon Carbide

Silicon Carbide (SiC) is an attractive semiconductor material for high-power and high temperature electron devices because it has excellent physical properties such as a wide bandgap, high breakdown voltage, high thermal conductivity, and high saturation electron drift velocity. However, there are many difficulties and problems in the process, which restrict the development of the SiC devices.When SiC devices operate at the high temperature and high power, thermodynamically stable ohmic contacts with low specific contact resistance are important, since parasitic resistances generally limit or even jeopardize device operation. To utilize the excellent properties of SiC in an electronic device, ohmic contact technology should be one of the most important process for SiC. There are several problems in ohmic contacts to SiC at present: (1) The component and thickness are not confirmed completely; (2) Time, temperature, ambience of the metallization annealing are full of the variety; (3) There is a considerable variation in the results of specific contact resistance with lack of reproducibility; (4) The physical mechanism and model of ohmic contacts to SiC are not clear.Although many groups have successfully demonstrated ohmic specific contact resistance about 10?6 ?cm2, most of them pay attention to the process parameters optimization based on a lot of experiments, and few focus on the physical mechanism and model of ohmic contacts which can be used to direct the process parameters optimization. Even for Nickel, which is the most widely used metal for fabrication of ohmic contacts to n-type SiC, the physical mechanism is still not very clear.Furthermore it is same to Al-Ti metallization which is used to form ohmic contacts to p-type SiC popularly.This study gives a series researches on ohmic contacts to SiC theoretically and experimentally. The research areas and main contributions are as follows. The theory and technique of ion-implantation to form the heavy doped regions in the SiC surface for ohmic contacts are studied. The energies, depth,deviation and distribution of P, N, Al ion-implantation for forming high doping region used for ohmic contact are simulated by MC simulator TRIM, also the process parameters such as energies and doses are designed. The parameters of ion-implantation (for N+, P+, Al+), the temperature, time, ambience, and cap of post-implantation annealing are designed. The crucible coated by poly-SiC is designed and fabricated which is used in post-implantation annealing. The Carbon cap for the SiC surface protection during...